Structures Found Only in Plant Cells

StructureDescriptionFunction
Cell wallRigid outer layer made of celluloseProvides structural support and prevents the cell from bursting when it absorbs water by osmosis (becomes turgid)
ChloroplastsGreen organelles containing chlorophyllSite of photosynthesis: absorb light energy to convert CO₂ and water into glucose and oxygen
Permanent vacuoleLarge central vacuole filled with cell sap (a solution of sugars, salts and pigments)Maintains turgor pressure to keep the cell firm. Stores dissolved substances.

Important: Not all plant cells have chloroplasts: root cells are underground and do not photosynthesise, so they lack chloroplasts.

Plant vs Animal Cell Comparison

FeaturePlant cellAnimal cell
Cell wallPresent (cellulose)Absent
ChloroplastsPresent in green partsAbsent
Permanent vacuoleLarge, central, permanentSmall, temporary (if any)
Cell membranePresent (inside cell wall)Present
ShapeRegular / rectangularIrregular / varied
Energy storageStarch granulesGlycogen granules

Exam tip: When comparing, always state what is present in both cells as well as the differences. Many students only list differences and miss marks.

Turgor and Plasmolysis

The cell wall and vacuole work together to maintain plant cell shape:

  • Turgid cell: the vacuole is full of water, pushing the cytoplasm against the cell wall. The cell wall prevents bursting. Turgor pressure keeps stems and leaves upright.
  • Flaccid cell: the vacuole has lost water, so turgor pressure is reduced. The cell becomes soft.
  • Plasmolysed cell (Supplement): in a concentrated solution, so much water leaves by osmosis that the cell membrane pulls away from the cell wall. The cell shrinks inside its wall. This is the beginning of wilting.

Animal cells do not have a cell wall, so in pure water they swell and can burst (lysis). In concentrated solutions, they shrink and become crenated.